<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>用transition 过渡做进度条</title>
    <style>
        .fhter {
            margin: 100px auto;
            width: 180px;
            height: 15px;
            padding: 1px ;
            border: 1px solid red;
            /* 小圆角做法取值为盒子高度的一半 */
            border-radius: 7px;

           
        }
        .son {
            width: 50%;
            height: 100%;
            background-color: red;
            /* 谁要做过渡就给谁添加transition过渡属性 */
            transition: width .7s;
        }
        .fhter:hover .son {
            width: 100%;

        }
    </style>

</head>
<body>
 <div class="fhter">
     <div class="son"></div>
 </div>
</body>
</html>